Egg Quality and a Woman's Age

A number of couples dealing with the issue of infertility sometimes fail to recognise one particular fact that may be the root cause behind their unsuccessful conception - the age factor.

Maternal age in particular, is an important consideration in order to determine the egg quantity and quality and, later, the embryo quality after fertilisation.

Women's Age and Eggs

Fertility decreases with a woman's age. This is because every woman has millions of eggs or, more specifically, follicles that mature into eggs inside her body when she is born.

By the time she reaches puberty, though, the number of these follicles drops down to about 300,000 to 400,000. During the monthly menstrual cycles, approximately 20 eggs start the journey to maturity but only one or two are finally able to complete this journey and are fit enough to be fertilised. These are the 'good' eggs.

Therefore, as you start aging, the number of eggs inside your body (egg quantity) and the number of good eggs that could have been fertilised (egg quality) keep depleting. Consequently, over time the chance of fertilisation also drops.

Egg quality and quantity are together known as the ovarian reserve and at any particular time, two women of the same age may have very different statistics in terms of this ovarian reserve.

But, in general, it has been found that the pregnancy rate begins to decline when people reach their the early 30s while the percentage of infertile couples starts increasing as follows:

By age 30, 7%

By age 35, 11%

By age 40, 33%

And at age 45, 87% of couples are infertile

Egg Quality

An egg is said to be of good quality if it has good normal chromosomes and it can easily combine with sperm to develop into an embryo. In order to fertilise the egg, sperm need to be healthy enough to travel and reach the fallopian tube (and yes, the quality of sperm also goes down as a man ages, the change is just more subtle and gradual).

However, an egg needs to be both healthy enough to fertilise and have the essential qualities necessary to divide and grow into a healthy embryo.

Eggs with abnormal chromosomes or those that just have the cytoplasm (the jelly-like material that comprises the cell) cannot ensure successful pregnancy.

Also, after fertilisation occurs, eggs need to have ample energy to grow and mature, which is supplied by the mitochondria present in the egg cells. If this energy is not sufficient then the embryo will eventually disintegrate, leading to miscarriage.

There are good and bad eggs from the very start in any female's body, but usually the number of eggs of superior quality are present at a higher volume at a younger age than after 30.

While analysing the egg quality, although age is an important factor, no two women can have the same number of good eggs. Egg quality is also affected by external sources like radiation therapy, smoking, chemotherapy and health conditions like endometriosis.

Egg Quality and Fertility

Poor egg quality may lead to infertility and repeated miscarriages due to one of these reasons:

Egg does not implant into the uterine wall after fertilisation

Egg implants but cannot grow due to insufficient energy

With increased age of the mother, the age of the eggs also increases and leads to abnormal chromosomes. Children born may have genetic abnormalities, like Down's syndrome.

This may also be a reason why certain fertility treatments, such as IVF and IUI, are repeatedly unsuccessful in older woman.